Author Options:

How UV resistant is wood? Answered

I'm making a USB solar charger intended to last 20 years. It will have no batteries inside, just a voltage reg and a zener diode.

The solar cells will be wired together under glass, not epoxy (for better lifespan). I want the frame to be made of wood, but how long will that last in direct sunlight?

This solar charger will contain no plastics, polymers, or resins...so my only choice for a frame is glass and wood.


PS. I chose wood because it is very opaque, and I reasoned that it may be fairly UV resistant... But IDK.


> UV's not the highest on the list
.  I would think that moisture, and the attendant rot, would be at the top of the list. If you can protect it from moisture (eg, killerjackalope's treated wood and/or paint/varnish/sealer), then UV shouldn't be a problem over the designed-for 20-year lifespan.

I'd agree with this. The issue is much more one of whether UV helping weather to break down the finish and thus let the wood be damaged by the other factors, than of UV acting directly on the wood.

Most paints do a fine job of withstanding UV. Transparent finishes have more trouble with it; for outdoor use where you care about appearance (such as a nice wood door), the usual recommendation is an oil-based spar varnish with high concentration of UV-blocking additives. (Spar varnishes don't resist mechanical wear as well as some others, but they stay more flexible which means they're better at handling wood expansion and contraction over wide temperature ranges.)

Wood will bleach, but it will resist sunlight for a very long time. Wasps & decay are more damaging.


Brazilian Ipe- a very dense, resinous jungle hardwood which in my experience is impervious to all that nature can throw at it.  It is pretty hard on tools as well so count on wiping out saw blades, drill bits, router bits, etc.


8 years ago

Environmentally friendly, weather resistant wood species are probably your best bet here. No wood is 100% UV resistant, but weather resistant species will develop an oxidized surface that increases it resistance to sunlight and weather.
If you want a low maintenance, long life, affordable wood. I would select in order, one of the following:

Western Redwood
Western Red cedar or pencil cedar
Siberian Larch

With wood it depends on what you treat it with, I'd say you might be well off going with pre treated wood and using some good coats of outdoor stuff, like shed or fence paint, with the best guarantee you can find, though 20 years is still a long stretch if it'll be outside all that time, it would need to be well sealed.

Really UV's not the highest on the list of priorities when it comes to wood's effective lifespan... 

I agree about the moisture.  There are wood building that have stood 100 years in a very dry climate even though they are exposed to sunlight every day.